Question regarding image pixelation

First, I apologize for the forum location, I was unable to locate a suitable area and figured maybe some GIMP Sr.'s might be able to help me out in determining the cause of an oddity between two images.
Also, I am not so much into image processing, but thought it would be interesting to learn.

Question:
What would cause two images to have different pixel colors in relative location with a white background when all that is changed is the zoom of the camera.

More detailed:
A friend of mine sent me a few images from the navy yard shooting (src: h t t p : / / media.heavy.com/gallery/aaron-alexis-new-photos/image_large-3.jpg - h t t p : / / media.heavy.com/gallery/aaron-alexis-new-photos/image_large-4.jpg [urls broken to avoid misclicks]) asking if I could clear up the messages a bit since they were pretty faded.
Currently the words on this side of the gun supposedly say "better off this way" and "my elf weapon".
When looking over it I started playing with the available wording since I couldn't find a high-def image and a lot of the text is really difficult to read with the currently released images, Starting with "MY ELF" turning it to MYSELF, burning the "Y" in way to an "R", random stuff like that. Just curious if words would fit differently when matching the lines up.
After messing with the color and finally inverting it one thing I noticed was the bottom right of the large-3 image and the number '5' (or s) with the pixels being mismatched and doesn't look like it belongs there. When comparing it with the -4 image it doesn't seem to add up.
The images appear to be edited (the ruler at the bottom has white lines over it) so manipulation was possible. After joking about conspiracy of the character '5' for a few minutes to lighten the mood given the situation these things came from, the actual question of what would cause the discoloration in the one image and the lack of detail in the second image has started to confuse me.

The best I can come up with is compression of the image. Most likely the finer details had been lost from them and this pixilation was caused by that compression. If the image was 'resaved' with those edits it might further the discoloration.
Is this a most likely scenario and would high-resolution/definition images be required to confirm, or is it possible to tell just from the current state of the images? If it is the case, how come it's only in this one location and not in both images?

Anyways, thanks for your time, I apologize for any epic fails in terminology.

Thank you both for the replies , sorry for the delay in getting back with you guys. Been a little swamped.
I played around with it some more and managed to get a few extra characters, still working on it though.

@ofnuts: good intel, thanks for that. I wasn't aware of how the algorithm picked an 8x8 frame. good to know for future reference . I've been on the lookout for better res images so I could compare. The 'conspiracy of the 5' gave us a few moments of laughter, that's for sure. I don't know wtf anyone would put a random 5 in there - the closest we could come up with was that the editor was trying to move the s from myself and accidently plopped it on the right hand side and just said screw it. .

@iforstyle007: If I ask a question - I like to hear an answer . I understand your concern though. I am still here! .
Playing with the thresh holds now and will see what I can come up with.

I think compression is the most likely scenario - now I kind of wonder why the hell someone would etch a 5 there. Ahh the questions. I'll keep playing around. If you want to post / email me your mods to the images: soko . splat @ gmail, it would be great to see what pros' can do .
Thanks again, both, for your time.